In a conventional electric stapler, it is general to use a throwaway type staple cartridge in which a whole staple cartridge is replaced when staples inside are used up. However, a staple cartridge of a refilling type refillable staple sheets has been spread, in order to achieve saving of resources and a reduction in wastes. A staple for refilling is distributed in a condition that staple sheets adhered with linear staples in parallel with each other are stacked and bound by a bundling strap of paper or a resin sheet, and accommodated in a paper box. A bundle of the staple sheets are taken out from the paper box and charged into a staple cartridge. The strap is removed and a cover of the staple cartridge is closed. Thereby, a mounting of the staple cartridge the electric stapler is completed.